CHAPTER – 2
Support and Movement
Irritability
The ability of an living organism to produce response against
any stimula are called Irritability it is also called Sensitivity.
Movement
Living organism shown the responses towards stimuli are called
Movement.
Support in Plant
Plants require proper strength and support it is necessary to
maintain their shape, increase in size and keep them straight and strong. The
support maintains balance. In plant body support is provided by two ways.
§ Turgidity in soft parts of plants
§ Mechanical tissues
Support Through Turgor Pressure
The living cell of epidemics, cortex and pith take in water by
osmosis. Thus an Internal hydrostatic pressure called “Turgor Pressure”, which
keeps them rigid and resistant to bending. If they loose turgidity stem wilts.
The turgor pressure is extremely important to maintain the turgidity in plants.
Support Through Supporting Tissue
In plants there are certain tissue called Mechanical tissues.
These tissue provide strength to the plant body.
1. Parenchyma
2. Collenchyma
3. Sclerenchyma
1. Parenchyma
Structure
§ Parenchyma is a simple tissue. It is composed of thin walled
spherical, oval or elongated cells.
§ They are with or without Intercellular spaces.
§ They are living cell.
Location
They are found in cortex, pith and epidemics, mesophyll region
of leaves.
Functions
Their function is synthesis of food and storage of food. They
may serve as a supporting tissue in soft plant due to internal turgor pressure.
2. Collenchyma
Structure
§ Collencym is a simple permanent tissue. It is composed of
rounded, oval or polygonal cells.
§ They are living cells with protoplasm.
§ Intra cellular spaces are absent and these cells thickened at
the corners due to deposition of cellulose and protopectin.
Location
These tissues are found in the dicot stem below the epidermis.
Functions
Collenchyma cell provide support to young herbaceous part of the plant. It elongate with the grow stem and leaves.
Collenchyma cell provide support to young herbaceous part of the plant. It elongate with the grow stem and leaves.
3. Sclerenchyma
Structure
§ Sclerenchyma is a simple permanent tissue. It is composed of
long, narrow thick walled cell.
§ They have no intracellular spaces.
§ They are dead cell without protoplasm.
§ A thick materials is deposit along the wall of cell called
pectin and lignin.
Location
Sclerenchyma tissues are found in xylem which are vascular
tissue.
Functions
They provide strength and Mechanical support to the plant parts.
Types of Sclerenchyma
There are two type of sclerenchyma
1. Fibers
2. Sclerides
1. Fibers
The sclerenchyma elongated cell with tapered ends. They are
tough and strong but flexible Fibers.
2. Sclerides
The variable often irregular in shape sclerenchyma are called
sclereids. Simple unbranched sclerids are generally called stone cell.
Secondary Growth
An increase in plant girth due to the activity of cambium ring
is called secondary growth.
Secondary Tissue
Tissues which are formed by the activity of cambium ring are
called secondary tissue.
Significance of Secondary Tissue
Cambium Ring
The ring of activity dividing cells responsible for lateral
growth in plant are called cambium ring.
Secondary growth occurs due to cell division in cambium ring.
There are two type
i.
Vascular Cambium Ring
The cambium present between xylem and phloem is called Vascular
Cambium Ring. The cell within the vascular bundles are called fusiform
initials.
Vascular cambium gives rise to two new tissues.
Secondary Xylem (Toward the inside)
Secondary Phloem (Toward the outside)
Growth Rings
The secondary Xylem causes most of the increase in stem
thickness. Over the year a woody stem get thicker and thicker as it vascular
cambium produce layer upon payer of secondary Xylem. These layers are visible
as rings.
Sap Wood and Heart Wood
The outer region of secondary wood is of lighter color and take
part in the conduction of water from root to leaf are called Sap Wood.
The inner region of secondary wood is dark brown in color and do
not take part in the conduction of water are called Heart Wood.
In most plant heart wood accumulate a variety of chemical such
as resins, oil, gum and tannins. Which provide a resistant to decay and insect
attack.
ii. Cork
Cambium Ring
The cambium ring present in cortex region and increase the
diameter of stem are called cork cambium ring.
Cork cambium cell divide and form new cells on both side.
Cork / Phellem ——> Outerside
Secondary Cortex ——> Inner Side
Cork /
Phellum
Cork is formed on the outer side by the cork cambium. Which is
an insulating layer prevent transpiration. Cork cell are dead and thick wall.
Secondary
Cortex
It is formed on the inner side by cork cambium. It is consist of
few layers of parenchymatous cells. They contain chloroplast.
Bark
Epidemics, lenticels and cork collectively called bark which is
the outer part of stem.
Callus
Another important function of the cambium is to form callus or
wood tissue on over the wound. The tissue are rapidly formed below the damage
surface of stem and root.
MOVEMENT IN PLANT
Definition
Any action taken by living organs to
reduce its irritability produce by stimuli are called Movement.
Type of Movement
There are two type of movement in plant.
1. Autonomic Movement
2. Paratonic Movement
1. Autonomic Movement
Movement which occurs due to internal stimuli factor inherent
inside the plant body itself are called Autonomic or spontaneous movement.
Types of
Autonomic Movement
There are three type of autonomic movement.
i. Locomotory Movement
ii. Growth Curvature Movement
iii. Turgor Movement
i.
Locomotory Movement
Movement of whole plant body or an organ or material within
plant cell from one place to another due to internal stimuli is called movement
of locomotion.
Example
The streaming movement of cytoplasm (Cyclosis).
Movement of chromosome during cell division.
ii. Growth
Curvature Movement
Change in the form and shape of plants or plant organs due to
the differences in the ratio of growth of different parts are called growth and
curvature movement.
Types of
Growth Curvature
There are two type of growth movement.
Nutation
Nastic
Nutation
The growth tip of young stem moves in zigzag manner due to
alternate changes in growth on opposite side of the apex. This type of growth
is called nutation.
Example
Movement of climber around any rope as found in railway crupper.
Nastic
When the process of growth occurs in different manner in the
parts of a plant and slow in other part it is called Nastic Movement.
There are two type of Nastic movement
Epinastic
Hyponastic
Hyponastic
Epinastic
When faster growth occurs on the upper side of the organ is known
as epinastic.
Hyponastic
When faster growth occurs on the lower side of the organ is
known as hyponastic.
iii. Turgo
Movement
Movement occur due to change in the turgidity and size of cells
as a result of loose or gain of water called Turgo Movement.
Example
Movement of leaves of touch me not.
2. Paratonic Movement
The movement occurs due to external stimuli are called paratonic
or Induce Movement.
Type of
Paratonic Movement
There are two type of paratonic movement.
i. Nastic Movement
ii. Tropic Movement
i. Nastic
Movement
The non directional movement of parts of plant in response to
external stimuli are called Nastic Movement.
Usually this movement occur in leaves or petals of flower.
Type of
Nastic Movement
There are two of nastic
a. Photonastic
b. Haptonastic
a.
Photonastic
The nastic movement occurs due to light are called photonastic.
Example
The flower open and close due to light intensity.
b.
Haptonastic
The nastic movement occurs due to the touch of any living
organism are called Haptonastic.
ii. Tropic
Movement
Tropic ——> Tropos mean “to turn”
The movement in response of growth of whole organ toward and
away from stimuli are called tropic movement. It is also known as directional
movement.
Type of Tropic
Movement
The main type of tropic movement are as follow
Phototropism
Geotropism
Chemotropism
Hydrotropism
Thigmotropism
Phototropism
Photo ——> Light Tropos ——> turn
The movement of part of plant in response to stimulus of light
are called phototropism.
Example
Positive phototropism in stem
Negative phototropism in root
Geotropism
Geo ——> earth Tropos —— turn
The movement of part of plant in response to force of gravity
are called Geotropism.
Example
Root display positive Geotropism and shoots negative geotropism.
Chemotropism
Chemo ——> Chemical Tropos ——> turn
The movement in response to some chemicals is called
Chemotropism.
Example
The hyphase of fungi show chemotropism.
Hydrotropism
Hydro ——> Water Tropism ——> turn
The movement of plant parts in response to stimulus of water is
called hydrotropism.
Example
The growth of root toward water is due to positive hydrotropism
and shoots negative hydrotropism.
Thigmotropism
Thigmos ——> touch Tropos ——> turn
The movement of plant parts in response to stimulus of touch are
called Thigmotropism.
Example
The movement in climber
SKELETON
Definition
The tough hard and rigid framework of the body which gives
particular shape and support to animal body are called Skeleton.
Human Skeleton
Endoskeleton present inside the human body. It consist of 206
bones. In man endoskeleton divide into two parts.
1. Axial Skeleton
2. Appendicular
1. Axial Skeleton
The skeleton composed of skull, sternum, ribs and vertebral
column are called Axial Skeleton.
i. Skull
The skull is made up of cranium and facial bones.
(Cranium)
The part of the skull consist of eight bones and form a box like
structure which protect the brain are called Cranium.
(Facial Bones)
The other bones of skull form face are called facial bones.
There are 14 facial bones such as check bones, upper jaws and lower jaws single
bone called dentary.
ii. Ribs
Cage
Ribs are semicircular bones attached on their dorsal side with
the vertebrae and on their ventral side with sternum.
Rib Cage is composed of 12 pairs of ribs. The lower two pairs of
ribs are called floating ribs because they do not attached with the sternum.
(Function)
The rib cage enclosed the chest cavity and protects heart and
lungs.
iii.
Sternum
The narrow rod shaped bones present in ventral wall of thorax are
called sternum. It is also known as breast bone.
iv.
Vertebral Column
A hollow spine in which spinal cord protected extend from skull
to pelvis are called V column.
(Bones of Vertebral Column)
The vertebral column consists of 33 bones called vertebrate but
due to fusion 26 bones are formed.
2. Appendicular
The skeleton system consist of pectoral girdle and hind limbs
and easy to move are called Appendicular skeleton.
Pectoral Girdle and Fore Limb
(Pectoral Girdle)
The girdle present in shoulder region and attach the arm to the
trunk are called Pectoral Girdle.
(Parts of Pectoral Girdle)
Pectoral girdle consist of two parts.
1. Scapula ——> board part
2. Clavicle ——> Collar bone which connects scapula with
sternum.
For Limb consist of
Humerus (1)
Radius (1)
Ulna (1)
Carpals (8)
Meta Carpals (5)
Phalanges (14)
Arrangement of Bones in Fore Limb
Arm: Humerus forms ball and socker joint
with scapular while at distal end humerus forms hinge joint with radius and
ulna.
Wrist: The radius and ulna at their distal
end from multistage with eight wrist bones called Carpals.
Hand: Five metacarpals from the frame work
of palm of the hand.
Digits: Five rows of the phalonges in fingers
are attached to the meta carpals. They support the finger.
PELVIC GIRDLE AND HIND LIMB
Pelvic
Girdle
The girdle present in lower region (hip region) and attached the
hind limbs (legs) to the vertebral column are called Pelvic gridle.
Structure
of Pelvic Girdle
Each pelvic girdle consist of large bone called Innominate. It
is formed by the fusion of three bones called Illium, Ischium and Pubis.
Hind Limbs
The hind limbs consist of
Femur (1)
Tibia (1)
Fibula (1) + Patella (1)
Tarsals (8)
Meta tarsals (5)
Phalanges (14)
Arrangement of Bones in Fore Limb
Thigh: Femur is the largest bones of the
body which forms a ball and socket joint with the Pelvic girdle.
Knee and Calf: At the distal end the femur from knee
joint with the proximal end of two parallel bones called tibia and fibula.
Ankle: The distal end of the tibia and
fibula form a joint with eight tarsals, which are also attached with five meta
tarsal bones of foot.
Digits: Five rows of the fourteen phalonges
of the toes are attached with meta tarsals.
Types of Skeleton
There are three main types of skeleton in animals.
1. Hydrostatic Skeleton
2. Exoskeleton
3. Endo Skeleton
1. Hydrostatic Skeleton
A fluid filled gastro vascular cavity or coelom act like a
skeleton are called hydrostatic skeleton.
Functions
Hydrostatic skeleton provides support and resistance to the contraction
of muscle so motility results.
Example
Hydrostatic skeleton found in annelids and other soft bodies
invertebrate.
Mechanism
of Working
The fluid filled body cavity of in these animals is surrounding
by layer of two types of muscles.
§ Circular Muscles
§ Longitudinal Muscles
When circular muscles contract and pressure comes on body fluid
by this process the body become elongated and hard.
When the longitudinal muscles contract the body becomes short
and thick due to the lengthen and shorten body move easily in the soil.
2. Exoskeleton
The hard non living external covering
that is secreted by the outer epidermal layer of animals are called
exoskeleton.
OR
The skeleton present outside the body
are called Exoskeleton.
Composition Of Exoskeleton
Exoskeleton are made up of different materials.
i. Silica
The exoskeleton of single celled diatoms made up of silica.
ii.
Calcium Carbonate
The exoskeleton of mollusks made up of lime (Caco3)
iii.
Cuticle
The exoskeleton of arthropods made up of hard, non living
substance called chitin. It is the complex of protein and carbohydrates. This
exoskeleton is dividing by soft flexible joints.
Functions
§ It provides a surface to which internal muscle can be attached.
§ It provides the protection and support to the body.
§ It is not help in locomotion but in arthropod. It helps in
movement due to joint.
Disadvantages of Exoskeleton
1. Due to exoskeleton the size of arthropods is short.
2. Growth is also limited because the exoskeleton is non living
and non growing.
3. Moulting or ecdysis: When the size of animal increase the
exoskeleton become short and it is separated from the body. It is replaced by a
new skeleton this process are called moulting.
3. Endo Skeleton
The skeleton present inside the body and made up of rigid living
connecting tissue bones and cartilages are called endoskeleton.
Functions of Skeleton
1. Support and Shape
It provides supporting frame work of the body, it gives the body
a particular shape.
2. Protection
Bones protect critical internal organs, such as brain spinal
cord, heart, lungs and reproductive organs.
3. Movement
Skeletal muscles attached to the bones help move the body.
4. Mineral Homeostasis
Bones serve as depository for calcium, phosphorus, sodium and
potassium. Bones can release or take up minerals through negative feed back
mechanisms to maintain the homeostasis.
5. Blood Cell Production
Red and white blood cells are produced in bone narrow.
BONES AND CARTILAGES
In vertebrate animals the endoskeleton contains two types of
connective tissues.
1. Bones
2. Cartilage
1. Bones
Bones is the most rigid form of connective tissue.
Structure
of Bones
Cell of bones are called Osteocytes. They secrete a gel like
matrix around them. It contains a network of collagen fibres but unlike
cartilages it is hardened by the deposition of Osteoblasts and crystals of
calcium phosphate. This process called Ossification or Calcification, takes
place in the presence of vitamin D.
2. Cartilage
Cartilage is the softer and flexible form of connective tissue.
Structure
of Cartilage
The living cells of cartilage are called chondrocytes. These
cells secrete flexible, elastic, non-living matrix. It consists of protein and
polysaccharides. The main protein in the matrix is collagen whose fibres run in
all directions and surrounds the chondrocytes. No blood vessels penetrate into
this cartilage.
FUNCTION
It covers ends of the bone at the joint and also supports the
flexible portion of nose, external ears and larynx.
Joint
The point at which two or more bones connect each other are
called Joint. The help in motality of skeleton.
Types of Joint on the Basis of
Movement
Joints are classified on the basis of the amount of movement
allowed by them, into three categories.
i. Immovable Joints
ii. Slightly Moveable Joints
iii. Freely Moveable
i.
Immovable Joints
The joints fit together tightly like the pieces to a puzzle.
These joints are called immoveable joints or fixed joints because they don’t
allow the joining bones to move.
Example
Example of fixed joint are the joints of skull in the term of
case to protect the brain.
ii.
Partially Moveable Joints
The joints which allow a little government is called partially
moveable joints or slightly moveable joints.
Example
Example of partially moveable joint is the attachment of ribs
with vertebrate. These joints permit out ribs to moves ups and down while we
breath.
iii.
Freely Moveable Joints
The joints which allow the movement in several directions is
called freely moveable joints.
Types of Freely Moveable Joint
Freely moveable joint that are present in human skeleton system
are
a. Ball and Socket Joint
b. Hing Joint
c. Pivot Joint
d. Sliding Joint
e. Gliding Joint
a. Ball
and Socket Joint
The joint which allow the movement in all directions even in a circle
is called ball and socket joint.
In this joint ball like head of the long bone of leg and upper
are fit into a cup like socket of girdle.
Example
Joint of hibs and shoulder
b. Hing
Joint
The joints that allow the movement in two directions such as
show the back and forth movement is called hing joint.
Example
Joint of fingers, elbow and knee.
c. Pivot
Joint
The joints which allow a twisting movement as well as side way
movement is called pivot joint.
Example
Joints of elbow and skull connected to the spine are the
examples of pivot joint.
d. Sliding
Joint
The joints which allow the bones to slides over one another and
show the movement in many directions are called sliding joint.
Example
Joints of wrist and ankle.
e. Gliding
Joints
The joints in which bones moves easily over one another in a
back and forth manner is called gliding joints.
Example
Joints of vertebral column that makes the back bone flexible are
the example of gliding joint.
Structure of Hing and Ball and Socket
Joint
§ At moveable joints the joining bones are held in place by strong
straps of connective tissues called Ligaments. Ligaments connect the bones to
each other and don’t allow the bones to slip and dislocate at a joint. As
ligaments stretch they allow the joints to move.
§ Highly moveable joints also need lubrication and cushioning to
prevent the adjoining bones crushing with each other. This is the function of
Synovial Cavities prevent around fluid the reduces the friction and keeps the
joint moving freely.
§ In addition cartilage pads at the end of bones act as shock
absorber and present bones from grinding together.
Deformities Skeleton
Human skeleton support and upright body. Sometimes in skeleton
certain disorders are developed which weak a skeleton system are termed as
Deformities of skeleton.
Causes of Deformities
The causes of deformities are
1. Genetic Disorder
2. Hormonal Disorder
3. Nutritional or Malnutrition
4. Physical Trauma
1. Genetic Disorder
i. Cleft
Palate
It is a genetic disorder in which cleft present in the palate
which interferes with sucking. It can lead to inhalation of food into the lungs
causing aspiration pneumonia.
ii.
Microcephaly
It is genetic disorder in which the skull becomes small sized.
iii.
Arithritis
Arthritis is the inflammatory or degenerative disease that
damage the joints. Osteo arthritis is the most chronic arthritis which is a
degenerative joint disease also caused by genetic defect.
2. Hormonal Disorder
The skeleton deformities of the bones caused by hormonal
deficiency.
i.
Osteoporosis
Osteoporosis mostly occurs in aged women, which is related to
decrease the level of estrogen hormone.
Symptoms
In osteoporosis, the bones become porous, thin and weak and
consequently easily breakable.
3. Nutritional Or Malnutrition
The skeleton deformities occur in the bones due to nutritional
deficiency.
Some of the nutritional disorders are
Some of the nutritional disorders are
i.
Osteomalacia
Osteomalacia is the softening of bones in which the bones
receive in adequate minerals and patient feels pain when weight is put on
affected bones. In this disease calcium salts are not deposited and hence bones
soften and weaken weight bearing bones of legs and pelvis, bend and deform.
ii.
Rickets
Rickets in children results in bowed legs and deformed pelvis.
It is caused by deficiency of calcium in diet or vitamin D deficiency. It
treated by vitamin D fortified milk and exposing sink to sunlight to cure
disorder.
4. Physical Trauma
Certain diseases caused by physical trauma are as follows
i. Disc slip
ii. Spondylosis
iii. Arthritis
iv. Sciatica
i. Disc
Slip
The backbone of body consists of many vertebrate. Between these
vertebrate special cartilage pad are present called Disc.
Functions
The discs act as shock absorber during walking, jumping, running
and lesser extend to the bend laterlly.
Disease
If due to physical trauma, the cartilaginous ring of disc
ruptures and displaces it is called Disc Slip.
Symptoms
§ Protrution presses spinal nerve and cause sever pain.
§ Unability to move.
§ Treatment
As a result of disc slip the person should use hard bed and should
take rest for long time.
Pain killer medicine should be used.
ii.
Spondylosis
Spondylosis is deformity of joints of two vertebrate
particularly of neck region when the space between two vertebrate becomes
narrow.
Symptoms
Due to spondylosis the nerves of spinal cord are pressed. It
causes pain in neck shoulder and upper parts of arm.
Treatment
§ In this condition a hard collar is used around neck.
§ Pain killer are used.
iii.
Arthritis
Arthritis is inflammatory or degeneration disease that damage
joints.
Causes
§ It may be due to
§ Hereditary
§ Viral Infection
§ Injury
§ Old age
Symptoms
§ It results in pain, stiffness, swelling of the joint.
§ Smooth and flexible cartilage between the bones of a joint is
denatured by the deposits of calcium, which makes the cartilages hard.
Treatment
Knee joint and hip joint can be replaced by artificial rubber or
plastic joint.
Sometimes it is treated by medicines and physiotherapy.
Sometimes it is treated by medicines and physiotherapy.
iv.
Sciatica
Sciatica is a nerve pain of hind limbs which occur when nerve of
sciatic plexus is being pressed.
Causes
§ It may be due to
§ Injury
§ Disc Slip
§ Improper administration of injection in the iliac vein.
Symptoms
It makes the leg highly painful and virtually immovable.
Treatment
The treatment of sciatica is very slow and prolonged. There is
no permanent treatment of this disorder.
Muscular System
Muscle made up to muscular tissue. A muscular tissue is a group
of specialized cells contain numerous filament of protein and perform a unique
functions to generates a pulling force.
There are more than 600 muscles in a human body and almost half
of body weight is due muscles.
Types of Muscles
The vertebrate possess three kinds of muscles
1. Skeleton Muscles
2. Smooth Muscles
3. Cardiac Muscles
1. Skeleton Muscles
The muscles that are attached with the skeleton and associated
with the movement of bones are called Skeleton Muscles.
Characteristics
§ Skeleton muscles are voluntary in function.
§ They can contract strongly and rapidly but fatigue quickly.
§ Skeleton muscle are striated muscles because they show alternate
dark and light band.
§ They are under the control of somatic nervous system.
§ Muscles are attached to the bones by special structure called
tendon.
Functions
With the help of skeleton muscles all the body parts can move.
2. Smooth Muscles
The simplest type of muscles which form all the internal hollow
body’s organs and it found in throughout animal kingdom, called smooth muscles.
Structure
Smooth muscles are structurally very simple muscles. They are
spindle shapes uni-nucleated cells. They are arranged in a sheet around the
hollow organs of the body.
Characteristics
§ These are unstriated muscles.
§ They are involuntary in function i.e. their movement is not in
our control but they are controlled by hormones and autonomic nervous system.
§ They contract more slowly than skeleton muscles but it can
prolonged for a long period of time.
Location
These muscles are found in the blood vessels, digestive tract
and many other organs.
Functions
§ Smooth muscles push the food to the digestive track.
§ They empty the urinary bladder.
§ They control the diameter of the blood vessels.
§ They also control the diameter of the pupit of eye.
3. Cardiac Muscles
The muscles which are present only inside the wall of heart are
called Cardiac Muscles.
Characteristics
§ These are striated muscles.
§ They are involuntary in function and fatigueless.
§ They contract and relax continuously in a rhythmic pattern. This
rhythmic contraction called heart beat.
§ Cardiac muscles have more mitochondria to continuous supply of
energy to the tissues of heart.
§ Cardiac muscles regulate by the sino atrial node (SAN) or pace
maker.
§ Heart is quite independent of nervous system for its contraction
and heart beat is generated by the cardiac muscles itself.
Structure
They are uninucleated or binucleated and branched to create a
meshwork of contractile tissue hence their fibres can not be separated like
that of a skeletal muscle.
Functions
The function of cardiac muscle is pump the blood.
STRUCTURE OF SKELETON MUSCLES
Muscle Fibre
Each skeleton muscle is actually a bundle of long and parallel
closely packed thread like multinucleated cells called the muscle fibres.
Size
Skeleton muscle fibres are huge cells. Their diameters is 10 to
100 mm.
Structure
o Muscle Fibre
Each muscle fibre is bounded by thin elastic membrane called
Sarcolemma. Similar to plasma membrane. Inside the sarcolemma, there is a
semifluid called Sarcoplasm.
Myofibril
Each muscle fibre contain a large number of many individual,
ultra microscopic contractile fine thread like structure called Myofibril.
The diameter of myofibril is 1-2 mm that run in parallel fashion and extend entire length of the cell.
The diameter of myofibril is 1-2 mm that run in parallel fashion and extend entire length of the cell.
Sarcomere
The myofibrils consist of smaller contractile units called
Sarcomere.
Structure
of Sarcomere
In each sarcomere a series of dark and light band are evident
along the length of each myofibril.
Microfilaments
The myofibril contains myofilaments or mocrofilaments.
Microfilament is made up of two types of filament.
i. Thick Filament
ii. Thin Filament
i. Thick
Filament
The central thick filaments extend the entire length of the
A-band. The thick filament which is about 16mm in diameter is composed of
myosin.
Structure
of Myosin
Each myosin molecule has tail terminating in two globular heads.
Myosin tail consists of two long polypeptide chain coiled together. The heads
are sometimes called cross bridge because they link the thick and thin
myofilaments together during contraction.
ii. Thin
Filament
The thin filaments extend across. The I-band and pathway into
A-band. Thin filaments are 7-8 mm thick and composed of chiefly actin molecule.
Structure
of Actin
The actin molecules are arranged in two chains which twist
around each other like twisted double strand of pcarls. Twisting around the
actin chains are two strands of another protein tropomyosin. The other major
protein in thin filament is troponin. It is actually three polypeptide complex.
One bind to actin, another binds to tropomyosin while third binds calcium ions.
I-Band
The area which appear light and contain only thin filament is
called I-Band.
H-Band
The area which appear bright and contain only thick filament is
called H-Band.
A-Band
The area of sarcomere which appear dark and contain both thick and
thin filament is called A-Band
MECHANISM OF CONTRACTION OF SKELETON
MUSCLES
There are two theories which explain the mechanism of contraction
of skeleton muscles.
1. Sliding Filament Theory
2. Cross Bridge Theory
1. Sliding Filament Theory
Introduction
H.Huxley and A.F. Huxley and their colleagues suggested a
hypothesis in 1954 to explain all even in muscle contraction this is called
Sliding Filament Theory.
Statement
According to this theory
The thin and thick filament of a
muscle fibre move together by sliding over each other. This is like sliding the
fingers of our hand between fingers of the other hand. The sliding of the
filaments is the reason that the muscle gets shorter and thicker.
2. Cross Bridge Theory
Introduction
When the bulbous heads end of the myosin filament discovered so the another theory explain the mechanism of contraction of muscle which show physical contact are called Cross Bridge Theory.
When the bulbous heads end of the myosin filament discovered so the another theory explain the mechanism of contraction of muscle which show physical contact are called Cross Bridge Theory.
Statement
According to this theory
The bulbarious head of thick filament
myosin become attached to binding sites on the actin filament. The cross bridge
are formed then contract to pull the actin filament towards center of sarcomere
and the muscles become contract.
Motor Unit
A set of all the muscle fibres innervated by the branched of the
single neuron and a single muscle fibre is made up of many motors units.
Controls of Muscle Contraction
The contraction of a muscle depends upon three factors.
1. Nerve Impulse
2. Energy
3. Calcium Ions
1. Nerve Impulses
Nerve impulse cause muscle contraction. The nerve impulses
(nerve message) are recieved from brain and spinal cord through motor nerves.
The muscles entirely depend upon these nerve impulses. When these impulses do
not reach to the muscles, they become fatigue. They loss stimulation and
contraction stops gradually.
2. Energy
Muscles also need energy for contraction. Energy required for
muscle contraction comes from food. The energy from food is stored in muscles
in the form of glycogen. It is transformed from glycogen to creative phosphate
and finally to ATP where it is stored and is readily available for use of
muscle.
3. Calcium Ions
Calcium ions play very important role in the initiation of
muscle fibre contraction. It is stored in sarcoplasmic reticulum.
§ When the nerve impulse reaches the acetyl choline is released.
§ Due to acetyl choline great number of calcium ions released from
Sarcoplasmic reticulum.
§ The calcium ions bind to troponin molecule and exposed the
active site of actin molecule.
§ The cross bridge is formed between actin and myosin and the
muscles become contracted.
§ After contraction has occurred the impulse stops, calcium ions
back into sarcoplasmic reticulum and the muscles fibres relaxed again.
Fatigue
Muscle fatigue is a state of
physiological unability to contract.
OR
When the muscles become functionless
it is called Fatigue.
Causes
ATP Deficit
Muscle fatigue results from relative deficit of ATP, not its
total absence.
Lactic
Acid Accumulation
Excess accumulation of lactic acid due to the breakdown of
glucose in absence of O2 and ionic imbalances also causes muscle pH to drop and
the muscle to ache hence causes extreme fatigue.
Recovery
When the heavy exercise stops and continues the supply the
excess oxygen to the fatigued tissues, which now break lactic acid into water
and carbon dioxide. Lactic acid is converted the fatigued condition of the
muscle is over. The amount of oxygen needed to remove lactic from the tired
muscle is called Oxygen Dept.
Abnormal Muscle Contraction
There are two common abnormal muscle contractions
1. Tetany
2. Cramps
1. Tetany
Tetany is a sudden involuntary contraction of striated muscle.
Causes
Tetany is caused by the low level of calcium in the blood.
Symptoms
It excites neurons which influence the muscles contract before
gaining the normal position of actin and myosin filaments, therefore it is
called abnormal function. In tetany there is continue contraction of muscle
fibres. Due to this continue contraction the Ca++ ions cannot be separated from
the sarcoplasm of muscles and continue contraction becomes very rapid, so it is
known as Tetany. If tetany occurs in respiratory organs, they may become
functionless.
2. Cramps
It is also known as titanic contraction of entire muscle. It
lasts for just few seconds or several hours, causing the muscles to become taut
and painful. It is most common in thigh and hip muscles, it usually occurs at
night or after exercise.
Causes
The main causes for cramps are as follows
§ Sugar level in blood is reduced
§ Sometimes dehydration occurs in the body.
§ Electrolytes (ions) are not in balance state.
§ Extra exercise is also harmful and causes cramps.
Treatment
Simultaneous squeezing and stretching the cramped muscle may
help.
Antagonisitic Muscles
The muscles work in pairs with one muscle working against the
other are called Antagonisitic Muscles.
Types of
Antagonisitic Muscles
On the basis of their function and affect they produce the
muscles are of following type.
1.
Protractor and Retractor
Protractor Muscle: These muscle pull the lower part of
limb in forward direction.
Retractor Muscle: These muscle pull the limb in
backward direction.
2.
Abductor and Adductor
Abductor Muscle: These muscle pull the limb away from
the body.
Adductor Muscle: These muscle pull the limb towards
the body.
3. Flexor
and Extensor
Flexor Muscle: They close the joint.
Extensor Muscle: These muscle open the joint.
Locomation in Protozoa
Protozoans are the unicellular animals. Then locomotion is
carried out by single called structures. These are of three types Pseudopodia,
cilia and flagella. These structures arise from the body surface and may also
help to capture the food.
1. Locomotion in Amoeba
Organs of
Locomotion
Locomotion in Amoeba is called amoeboid movement. Amoeboid
movement takes place by means of Pseudopodia.
Method of
Locomotion
The pseudopodia are finger like projections in the direction of
movement. After the formation of pseudopodia the Amoeba attaches with the
substratum and pull the body in the forward direction.
The exact mechanism of pseudopodia formation is still not known.
The exact mechanism of pseudopodia formation is still not known.
2. Locomotion in Euglena
Organs o
Locomotion
Euglena moves with the help of flagellum.
Methods of
Locomotion
As the flagellum is whipped backward the organism moves forward.
However, when flagellum moves forward the Euglena does not move backward.
Flagellum is at is anterior end of the body and pulls the organism forward.
Wave of activity generated by itself and they pass in spiral fashion from its
base in spiral fashion from its base to its tip.
Euglena increases amplitude and velocity. The activity of the flagellum caused the body of Euglena to rotate forward abouts its axis.
Euglena increases amplitude and velocity. The activity of the flagellum caused the body of Euglena to rotate forward abouts its axis.
Euglenoid
Movement
In this mode of locomotion, a wave of contraction and expansion
passes from the anterior to posterior in entire body. The contraction and
expansion is brought by the contraction of protoplasm. The body becomes shorter
and wider first at the anterior, then in the middle and finally at posterior.
3. Locomotion in Paramecium
Organs of Locomotion
Paramecium moves with the help of Cilia. The movement by cilia
is called Ciliary movement.
Structure
of Cilia
Cilia are short fine thread-like extensions of the cell
membrane.
Method of
Locomotion
The locomotion in paramecium take place by the beating of these
cilia. The beating action occurs in two strokes.
Effective
Strokes
During effective stroke the cilia become rigid and bent backward
but obliquely propel the animal forward.
Recovery
Strokes
During recovery stroke the cilia become softer and returns to it
original position.
As a result of effective and recovery stroke paramecium swims
against water. The body move forwards.
4. Locomotion in Animals
i.
Locomotion in Jelly Fish
Jelly fish has umbrella like body which floats on the surface of
water at the mercy of waves. However it can swim slowly by muscular
contraction.
Mechanism
In jelly fish the water enters in the umbrella like body (Bell).
Then the muscle of the body contract and water is forced out in a jet, as a
result animal movement is known as “Jet Propulsion”. The jelly fish moves in
jerks in the direction opposite to the expelled water.
ii.
Locomotion in Snail
Organs of
Locomotion
Snail crawl or move very slowly by “foot”.
Mechanism
The foot of snail produces a wave of muscular contraction on its
under side. This wave is from front to rear and animal is pushed forward. The
movement is lubricated by slime which is poured on land immediately from glands
below the mouth.
iii.
Locomotion in Star Fish
Organs of
Locomotion
Starfish moves with the help of tube feet. The tube feet are
present on both sides of radial canal that extends up to the tip of arm.
Structure
of Tube Feet
The tube feet are hollow muscular and are like rubber bulb of the
medicine dropper. The tube feet consist of three parts.
§ Ampula
§ Podia
§ Sucker
Mechanism
In starfish locomotion is controlled by a special water vascular
system. Water is drawn into the body through a small opening and is passed
through a ring canal to large number of hollow muscular tube feet. The tube
feet extend when water is pumped into them then they fix themselves by suction
cup (sucker) with some object. When sucker muscle contract the water is pushed
back into the ampullae, making the tube feet flaccid losing the grip and the
starfish is pulled forwards.
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